1. Field of the Invention
The present application relates, in general, to apertures for the control and/or measurement of light.
2. Description of the Related Art
An aperture is an opening through which light energy can pass. An aperture can be thought of as an opening at a selected point in an optical system that determines the size of the bundle of light rays that traverse the system. Virtually all optical systems incorporate one or more apertures. For example, apertures may be used, in various optical systems, to define a field-of-view (e.g., as used in telescopes, microscopes and other imaging optics), define beam convergence/divergence and uniformity (e.g., as used in collimating optics), or control the size of an image (e.g., as used in some reflectance, transmittance, or detector response accessories).
Within optical systems, apertures often appear in what are known in the art as optical “trains”. An optical train is typically used to control and/or measure light, and optical systems typically have at least one, and sometimes several, optical trains. For sake of illustration, an optical train can be treated as having three main components: a light source, a controlling device (e.g., an aperture), and a detector. These components generally are arranged in a serial manner.
With reference now to the figures, and in particular with reference now to FIG. 1A, shown in side plan view is an optical train 100 consisting of a light source (e.g., a lamp) 102, an aperture (e.g., a cylinder drilled in a piece of sheet metal) 104, and a detector (e.g. a photometer) 106. Although the aperture 104, when shown in perspective view (see FIG. 1B), appears circular in shape, those having ordinary skill in the art will appreciate that apertures can be quite varied in shape (e.g., circular, square, slit(s), star, or other various shapes).
FIG. 1A represents the “ideal” case, in which it is assumed that the surface 108 facing the light source 102 is totally absorbing of light, and hence that the “signal strength,” or intensity, of the light detected by the detector 106 is solely indicative of the signal strength of the light source 102. When optical systems are designed analytically, it is most common for the system designers to perform the analytic calculations assuming the idealized case in their calculations. Unfortunately, actual systems rarely tend to approach the idealized case.
Referring now to FIG. 2, illustrated is an optical train representative of an actual, as opposed to idealized, related-art system. As shown, in an attempt to approach the idealized case, the surface 108 facing the light source 102 is treated or prepared to be “light absorbing” (e.g., is painted black). However, also as shown, in the related art such preparations often fall short, and instead what happens is that a measurably significant amount of light 200 is reflected back from the surface 108. Depicted is that a portion of this reflected light is subsequently re-reflected such that it makes its way through the 104 aperture and is thereafter detected by the detector 106.
Those having ordinary skill in the art will recognize that the re-reflected light energy will often tend to give an indication that the light source 102 is more powerful than the light source 102 actually is (indicated in FIG. 2 by making the triangles representing light energy larger than they appear in FIG. 1A). Accordingly, such re-reflected light, when considered from the standpoint of measuring the intensity or signal strength of the light source 102, is essentially “noise.” Those having ordinary skill in the art will also recognize that such noise often clashes with analytical designs and calculations which assumed no, or measurably insignificant, noise. This resulting clash, at best, requires considerable subsequent work to make analytically designed systems function as desired, and, at worst, requires that the analytically designed systems be redesigned with assumptions more close to an actual system such as that depicted in FIG. 2.
Consequently, it is apparent that a need exists in the art for a method and system which substantially decreases noise due to reflections from one or more surfaces below the level of that manifested in comparably sized and situated related-art systems.